What is I-cell Disease (Type II Mucosolipidosis)?
I-cell disease (type II mucosolipidosis) is a disease that is associated with impaired cleavage of mucopolysaccharides and sphingoglycolipids. In this regard, it is clinically manifested by symptoms characteristic of mucopolysaccharidosis and Niemann-Pick disease (splanchnomegalia, rough facial features, mental retardation and neurological disorders).
Causes of I-cell Disease (Type II Mucosolipidosis)
The disease is caused by dysfunction of lysosomal hydrolases. The type of inheritance is autosomal recessive.
Pathogenesis during I-cell Disease (Type II Mucosolipidosis)
In fibroblasts of patients with I-cell disease, there is a deficiency of b-hexosaminidase, arylsulfatase A and b-glucoronidase, and in body fluids (serum, urine, cerebrospinal fluid), lysosomal hydrolase activity is increased. Cleavage of mucopolysaccharides, glycolipids and glycoproteins is reduced. It is believed that the absorption of enzymes by the lysosome is disturbed due to changes in posttranslational modification. In the molecules of these enzymes, there is no mannose-6-phosphate marker group recognized by a specific receptor that provides for the intracellular transport of enzymes to lysosomes. The defect of the lysosomal enzyme marker center is due to the insufficiency of the phosphotransferase localized in the plate complex of the Golgi apparatus. Electron microscopy of fibroblasts determines unusual cytoplasmic inclusions. The same changes are noted in the axons of the peripheral nerves, liver, renal glomeruli and the epithelium of the renal tubules.
An autopsy study reveals a thickening of the heart valves, myocardial infiltration with vacuolated fibroblasts and proliferation of the connective tissue of the aortic wall.
Symptoms of I-cell Disease (Type II Mucosolipidosis)
Already since birth, hepatomegaly, grotesque facial features, gum hypertrophy, kyphoscoliosis, widening of intercostal spaces are noted. Congenital dislocation of the hip, hernia, bilateral clubfoot; expressed contractures of the joints. Respiratory viral infections are common. The skin is rough, thick, the skin around the eyes is swollen, there is a slight clouding of the corneas. There is a progressive delay in physical and psychomotor development. Children usually die before the age of 5 years.
Diagnosis of I-cell Disease (Type II Mucosolipidosis)
The diagnosis is made on the basis of the clinical picture, differences in the activity of lysosomal hydrolases in body fluids and fibroblasts. The differential diagnosis is carried out with Hurler syndrome (mucopolysaccharidosis type I), in which the excretion of mucopolysaccharides with urine is within normal limits.
Treatment of I-cell Disease (Type II Mucosolipidosis)
The treatment is not developed. To prevent the birth of a sick child, prenatal diagnosis of I-cell disease is performed, which is possible only in specialized clinics.